EP1954460B1 - Process for producing a reinforcing material from strand-shaped filaments which are impregnated and enveloped with thermoplastic - Google Patents

Abstract

In a process to make a strengthening material, filaments produced in a hotmelt spinning assembly are combined in roving or a tape and are impregnated with a thermoplastic agent to form a matrix. The hotmelt spinning assembly discharges the matrix as a foil, which is then drafted. In the drafting process, the thermoplastic material is stretched, while the fibers are fractured. The foil may then be cut into strips of width typically 3 - 30 mm.

Description

The invention relates to a method for the production of reinforcing material from strand-shaped filaments, which are impregnated with thermoplastic and coated.

For many years, attempts have been made repeatedly to produce reinforcing material made of reinforcing fibers and thermoplastic matrix, wherein in particular the use of carbon fibers causes considerable difficulties, since they severely limit, for example, the drapability of the reinforcing material thus produced.

In the DE 198 52 159 C1 For example, there is proposed a process for fiber impregnation and production of fiber-reinforced thermoplastic matrix hollow bodies. The process for producing wound hollow bodies with a thermoplastic matrix has the task of processing textile semi-finished textile products which can be processed in the winding process, such as roving, yarn, filament, ribbon, fabric, etc., to be stripped from a spool, impregnated in a jacketing die with thermoplastic melt supplied by a meltdown extruder, and laid down on a rotating mandrel. Thus, this known method consists only in impregnating semi-finished reinforcements with the thermoplastic matrix and depositing them on a rotating mandrel.

From the EP-A-395 036 For example, a process is known in which a polymer-impregnated tow is stretched such that the reinforcing fibers are stretch-broken. For this purpose, the tow is guided in a zone generating a tensile stress and the polymer is heated, so that the reinforcing fibers are then break-broken.

The invention is based on the object to provide a reinforcing material of reinforcing fibers and thermoplastic matrix, in which the reinforcing fibers have gained the property by stretch breaking, can be stretched and deformed in a further drawing process without losing the original orientation.

This object is achieved by a method having the features of claims 1 or 2.

Advantageous embodiments are explained in the subclaims.

Hereinafter, the term "roving" is understood to mean filaments arranged in parallel, preferably continuous filaments.

The term "ribbon" is understood to mean a relatively small group of individual filaments.

The term "expansion-breaking method" or "stretch-breaking method" or the term "stretch-breaken" which is customary in practice today is understood to mean a method consisting of relatively coarse filament rovings by tensile stress between a clamping effect exporting pairs of rollers, in which preferably the next following always runs at a higher speed than the preceding, the continuous filaments in lengths of z. B. 40-400 mm to break irregularly and to stretch a sliver with much finer final titer.

In the following, the term "organosheet" is used. So-called "organosheet" consists of fiber-reinforced thermoplastic. It is produced in a continuous process. In the catchment area of an isobaric, heated double belt press is z. B. thermoplastic powder or thermoplastic film placed between the reinforcing layers, heated and pressed between the filaments.

In other words, the invention proposes that the filaments combined into a roving or a ribbon are optimally impregnated with thermoplastic in a melt-spinning apparatus, that is to say the thermoplastic matrix is achieved, the melt-spinning apparatus spinning this matrix in the form of a film is then stretched, wherein the thermoplastic portion is stretched and the Armierungsanteil is broken. The film can be cut into narrow strips, these strips may have, for example, a width of 5 - 30 mm. The inserted ribbon can already be broken.

According to the invention, it is therefore proposed that the strain-breaking process and the impregnation and the stretching be carried out in one operation, whereby a cost-effective manufacturing process is provided.

The narrow strips produced in this way can be used in various surface-forming methods, i. H. they can be woven, forfeited, intertwined, or even a clutch can be made.

From the produced so-called fabric then an "organosheet" can be consolidated, for. B. by heating to the softening or melting point of the thermoplastic matrix used, wherein simultaneously or subsequently a pressing operation takes place, in which case subsequently the organosheet can be later or simultaneously converted to the desired finished part.

In this case, it is possible to proceed in such a way that the textile surface formed from the textile strips, ie the organosheet, is placed in a press mold in one or more layers and heated and converted into the finished part.

The obtained by the method according to the invention by the stretch breaking reinforcement with the thermoplastic matrix can be used as a follie or strip z. B. in a pultrusion process to profiles further processed.

By "pultrusion process" is meant a process for pultrusion of fiber reinforced plastics in which the resin impregnated reinforcing material is continuously drawn through a die of the desired profile, obtaining its final shape and simultaneously curing.

Particularly suitable for use as reinforcing fiber element carbon fibers are used. Until now, this was only possible to a limited extent because, for cost reasons, this material could only be used to a limited extent as a reinforcing material. Now it should be considered that z. For example, for producing a reinforcing element as a starting material, normally a 12K (about 800 tex) or 24K (about 1,600 tex) (tex means: g / 1000 m). Carbon roving would be used. For example, the commercial price for a 12K or 24K roving is currently € 23 / kg.

But if you go z. For example, from a roving with 80,000 continuous filaments, a so-called 80K carbon roving, with a single titer of about 0.067 tex, ie a total of 5,360 tex, so in the stretch breaking process with a stretch of 6- to 7-fold a sliver of approx 800 tex produced (tex means: g / 1000 m). Thus, a carbon material or other fibrous material is available which has the desired drapability after consolidation with a thermoplastic matrix. The starting material for the 80K carbon material given in the example above is only € 14.00 / kg compared to a 12K or 24K roving. The cost advantage is therefore already at 40%.

According to the invention, it should be noted that stretching does not involve stretching of the individual fibers, but rather a sliding past the non-uniformly-length-broken filaments into the fiber-reinforced foil strip which is ultimately lighter in weight per unit length. The filaments broken by the process described no longer form continuous fibers but no measurable fiber damage can be detected by the treatment. This results in later laminate only increased elongation values, so that thereby the condition for the use of the reinforcing material is created.

In the foregoing, the production of a reinforcing material has generally been mentioned. Field of application is also the production of a rod-shaped reinforcing material for the construction industry.

This relates both to the production of a single rod as well as the further processing of such, a thermoplastic matrix having fiber-reinforced element to welded together grid surfaces, as they can be used for the construction industry. Here, the grid can be made in appropriate manufacturing facilities, as z. B. is also known in the steel mesh.

However, this design of the reinforcing material has the further advantage that even a light welding of the individual bars to the grid is possible.

Claims (11)

1. Process for producing a reinforcing material from strand-shaped filaments which are impregnated and enveloped with thermoplastic, characterised in that the filaments combined to form a rove are optimally impregnated in a melt-spinning device to form a thermoplastic matrix by spinning and stretching it in the form of a film, thus stretching the thermoplastic component and in doing so breaking the reinforcing component.
2. Process for producing a reinforcing material from strand-shaped filaments which are impregnated and enveloped with thermoplastic, characterised in that the filaments combined to form a small ribbon are optimally impregnated in a melt-spinning device to form a thermoplastic matrix by spinning and stretching it in the form of a film, thus stretching the thermoplastic component and in doing so breaking the reinforcing component.
3. Process in accordance with claim 2, characterised in that the small ribbon itself is broken by stretching.
4. Process in accordance with claim 1 or 2, characterised in that the film is cut into narrow strips.
5. Process in accordance with claim 4, characterised in that the narrow strips are used in various surface-forming processes, such as weaving, knitting, braiding and the production of interlaid scrims.
6. Process in accordance with any of the foregoing claims, characterised in that the film or the textile surfaces can be consolidated individually or in a number of layers and later thermally re-formed into a so-called organo-sheet by heating either to the softening or melting point of the thermoplastic matrix used and a simultaneous or subsequent pressing operation.
7. Process in accordance with any of the foregoing claims 1 to 5, characterised in that the film or the textile surfaces formed from the strips can be laid in one or more layers in a compression mould, heated and re-formed to make a finished part.
8. Process in accordance with any of the foregoing claims 1 to 5, characterised in that the film or the strips are worked into profiles by a pultrusion process.
9. Process in accordance with any of the foregoing claims, characterised in that filaments from the carbon fibre, fibreglass, ceramic fibre or aramid fibre, etc., group are used.
10. Process in accordance with one or more of the foregoing claims, characterised in that stretching does not mean that the individual fibres are stretched but rather that the filaments which are broken to uneven lengths slide past one another to form a strip of film which is lighter per length unit and which ultimately corresponds to the degree of stretch.
11. Welded latticed surfaces manufactured from the rod-shaped reinforcing material in accordance with one or more of the foregoing process claims and used for reinforcement in the building industry.